In order to make numerical information retrievable in a natural language, a retrieving device needs to cope with numerical expressions.
With a prior-art numerical information retrieving device, as in a technique stated in, for example, JP-A-7-200583, a numerical/temporal expression containing a relative expression can be handled as an input sentence by taking note of contextual information and information on the reference and range of the temporal/numerical expression. With such a prior-art numerical information retrieving device, by way of example, the “next year” is completed or corrected as being “1991” relative to “1990”, Likewise, the “next” is completed or corrected as being the “fourth place” relative to the “first to third places”.
The prior-art numerical information retrieving device, however, cannot cope with representations such as units, numerical representations of various references, or numerical expressions of various references.
By way of example, although the “increase of 100 dollars” relative to “1000 dollars” may be simply completed or corrected as being “+100”, the “increase of 1 centimeter” or “increase of 1 mm” relative to “1 meter” cannot be completed or corrected unless numerical conversion is first performed.
The present invention has for its object to solve such a problem in the prior art, and to provide a numerical information retrieving device with which a user can retrieve numerical information without caring about numerical representations or unit systems.